The purpose of this project is to develop a noninvasive technique for the estimation of pulmonary artery pressure based recordings obtained with a prototype doppler instrument developed by the Cardiovascular Pulmonary Research Laboratory at the University of Colorado Health Science Center. During Phase 1 of the project the investigators will focus on the analysis of the relationship between a number of changes in velocity and timing thought to occur with elevated pulmonary artery pressure and pulmonary artery pressure measured invasively during cardiac catheterization. The focus of these analyses will be to provide a combination of parameters which predict pulmonary artery pressure in a variety of individuals under a variety of conditions. The project will focus on recordings previously obtained with the prototype instrument, although new data will continue to be collected. Retrospective and prospective studies of Doppler scans as compared to catheter data are to be performed in an attempt to relate Doppler signal characteristics to pulmonary artery pressure. If reliable relationships can be found the signal processing algorithms will be incorporated into a dedicated instrument during a Phase II effort. The approach appears promising although the number of variables to be investigated is large for a six month study.